It is strange that the appointment appears as tentative. For an appointment to appear as tentative the outlook sniffer would need to see the appointment in the inbox. So this would tell me that the appointment does arrive in the inbox.
I take it the execs have "send meeting responses to the delegates not to me" selected ?
Are the delegates accepting meeting requests on behalf of the users ?
If you remove the user from the bes server does the calendar function properley ?
I have seen this in the past, If a delegate goes into the users calendar and right clicks the appointment and accepts the appointment, the original meeting request is still in the users inbox. If the user then clears down the inbox the appointment is deleted.
I would set the following reg key on each delegates registry.
HKEY_CURRENT_USER\Software\Microsoft\Office\10.0\O utlook\Options\General\DelegateWastebasketStyle DWORD to value 4.
If you set this key you also need to make sure that delegate also has author access to the execs deleted items folder. see hotfix KB202517
Setting this key means if a delegate accepts execs meeting request the accepted meeting request goes into the execs deleted items not the delegates deleted items folder. When the blackberry sees the accepted meeting request in the deleted items folder it process it correctly.
Also I would install outlook 2003 SP2 this contains fixes for missing calendar appointments to with outlook caching.
I would also update CDO.DLL to the latest version on both exchange and bes. There have been lots of post SP2 Exhange CDO hotfixes been released that fix problems with missing calendar appointment.
the last 2 lines are links to microsoft CDO fixes kb9130993 and 911928. A recurring meeting is not removed from an Outlook 2003 userxxx226;xxx8364;xxx8482;s calendar when the meeting is created by using CDO in Exchange Server 2003 An appointment does not appear on the attendee's calendar when you use a CDO 1.21 program to process the appointment in Exchange Server 2003